Answers Database


4000ex/xl : Can bufge and bufclk be driven in parallel?


Record #4204

Problem Title:

4000ex/xl : Can bufge and bufclk be driven in parallel?


Problem Description:
Urgency: Standard

General description:
Databook stated that bufge and bufgls can be driven in
parallel.
How does this work?


Solution 1:

You can drive bufgls and bufge in parallel by connecting
an IPAD to both bufgls and bufge in parallel.

This will translate to the following configuration in EPIC:

ipad -----> bufg ----> bufge ---->logic
              |
              |-> bufgls---->logic

No additional delay will be introduced by the extra bufg
front of the parallel bufge and bufgls.

The delay stated in databook for both bufgls and bufge has
already included the bufg.

An example of the timing report is as follows:

Path CLKP to O1 contains 3 levels of logic:
Path starting from Comp: P4.PAD
To		     Delay type 	Delay(ns)  Physical Resource
						   Logical Resource(s)
-------------------------------------------------  --------
P4.CLKIN	     Tclkin		   0.010R  CLKP
						   CLKP
BUFG_WNW.I	     net (fanout=1)	   0.010R  CLKP
BUFG_WNW.O	     Tclk		   0.000R  CLKP.BUFG
BUFGE_WNW.I	     net (fanout=2)	   0.000R  CLKP.BUFG
BUFGE_WNW.O	     Tclk		   0.000R  $I16
CLB_R1C10.K	     net (fanout=1)	   2.558R  CLK1
-------------------------------------------------
Total (0.010ns logic, 2.568ns route)	   2.578ns
      (0.4% logic, 99.6%% route)

------------------------------------------------------------
Path CLKP to O2 contains 3 levels of logic:
Path starting from Comp: P4.PAD
To		     Delay type 	Delay(ns)  Physical Resource
						   Logical Resource(s)
-------------------------------------------------  --------
P4.CLKIN	     Tclkin		   0.010R  CLKP
						   CLKP
BUFG_WNW.I	     net (fanout=1)	   0.010R  CLKP
BUFG_WNW.O	     Tclk		   0.000R  CLKP.BUFG
BUFGLS_WNW.I	     net (fanout=2)	   0.000R  CLKP.BUFG
BUFGLS_WNW.O	     Tclk		   0.000R  $I17
CLB_R18C20.K	     net (fanout=1)	   1.776R  CLK2
-------------------------------------------------
Total (0.010ns logic, 1.786ns route)	   1.796ns
      (0.6% logic, 99.4%% route)

Note: clkp is the net connecting ipad to the bufgs.
       'R' next to the delay number means it is a rising edge
       delay.





End of Record #4204 - Last Modified: 07/13/98 16:26

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